NASA struggling with robot power trouble because of design flaw

MARCIA DUNN

Published 7:00 pm, Thursday, March 13, 2008

AP Aerospace Writer

The space station's new robot remained without power because of a cable design flaw Friday as flight controllers devised yet another plan to get electricity flowing to the machine's various joints and electronics.

Engineers believe the problem is with a cable that wasn't designed properly. Engineers on the ground put in the wrong circuitry; that was enough to create a roadblock in power and data to the robot named Dextre.

The robot had its hands attached to its arms during a spacewalk that ended well before dawn Friday. But the next spacewalk on Saturday night, to hook its 11-foot arms to its torso, could be delayed or changed if power doesn't start flowing.

To try to resolve the problem, Mission Control instructed the astronauts aboard the linked space shuttle and space station to attach the station's robot arm to Dextre late Friday night and get power flowing that way. The problem cable is in Dextre's transport bed, or pallet, which the astronauts are using as a staging area to put the robot together.

Dextre cannot be completely assembled or tested without power to heat its joints and electronics.

The Canadian-built robot _ which cost more than $200 million _ is intended to be a helper for spacewalking astronauts. It ultimately could take over some spacewalking jobs, saving time for space station crews while reducing their risk.

Engineers initially suspected the problem might be with a timer and require a simple computer software patch, but ruled that out. They tried the patch anyway, and it did not work.

Mission Control should know within minutes whether the temporary robot-arm solution works, said LeRoy Cain, chairman of the mission management team. Once it's completely assembled early next week, the robot will be removed from its transport bed. From that point on, it will be powered from its various attachment points directly on the international space station.

Endeavour and its seven-man crew delivered Dextre _ lying in pieces on its transport bed _ to the space station. On Thursday, it was attached to the exterior of the orbiting outpost.

Cain said he did not know whether the Canadian Space Agency or NASA was at fault _ or both. Preflight testing did not catch the problem because the circuitry between the ground equipment and cable was a proper match; in space, it's not.

He promised a full investigation "to run this to ground and understand exactly what happened and how and why."

Toward the end of the seven-hour spacewalk that began Thursday night, astronauts attached the first segment of Japan's Kibo lab, a storage compartment that is 14 feet long. The $1 billion lab itself will fly to the space station in May, aboard shuttle Discovery.

Late Friday, Japanese astronaut Takao Doi made a grand entrance into the new compartment.

"This is a small step for one Japanese astronaut, but a giant entrance for Japan to a greater and newer space program," Doi said.

Five spacewalks are planned for Endeavour's nearly two-week visit, the longest ever by a shuttle.

On Friday, mission managers concluded that Endeavour's heat shield made it through Tuesday's liftoff in good shape and formally cleared the shuttle for re-entry on March 26.